The Central Laboratory for Human Embryology, funded by the National Institutes of Health for 30 years, is the major national resource for the collection, study, description and distribution of human embryonic and fetal tissues. This effort has resulted in the publication of approximately 1000 publications from intramural and extra mural sources and Laboratory publications serve as standards for human prenatal growth, development and dysmorphology. Because of the experience and expertise of its personnel, the Central Laboratory for Human Embryology collects, characterizes, stages, identifies, processes and distributes human embryonic and fetal tissues within minutes of delivery. This efficiency enables the laboratory to maximize the usefulness of valuable but often fragmented specimens by distributing many different tissues from individual embryos to multiple investigators across the United States. The efficiency of the Central Laboratory for Human Embryology is due, in part, to its long-standing relationships with regional clinics and hospitals. In exchange for participating in our program, clinic personnel promptly receive reports of autopsy findings that are often useful in genetic counseling and/or confirmation of the findings of prenatal diagnostic procedures. The annual collection and analysis of 3500 unselected embryos and fetuses, combined with years of experience in embryology and teratology enable us to perform a surveillance function by monitoring for changes in types or incidence of congenital defects present in abortuses. Removal of restrictions on the use of federal funds to study the therapeutic utility of conceptual tissue has dramatically increased research in fetal transplantation. New techniques in molecular biology have further increased the demand for human embryonic and fetal tissue samples. Meeting these demands require& a reliable source of viable, functional tissue that has been precisely staged, characterized and identified. Long-standing relationships of local hospitals and clinics with the Central Laboratory for Human Embryology, coupled with the expertise of Laboratory personnel, ensure a virtually unlimited supply of conceptual tissues for biomedical research. This expertise is evidenced by the many strong letters of support included with this application.